In the past, numerous attempts have been made to develop machines for effectively and economically removing the internal bead which is formed by the longitudinal seam welding of tubing.
In the Siegerist U.S. Pat. No. 2,712,249 an apparatus is disclosed which employs a pair of reciprocating hammers and an anvil positioned inside the tubing which cooperate to hammer the bead flat. The anvil is attached to a resilient cable which permits it to move a short distance along with the tubing as it travels and then to be returned to the proper position between the hammers. As a result, the anvil is properly positioned for each successive hammering blow.
In the C. D. Preusch U.S. Pat. No. 3,494,165, an apparatus is disclosed in which a plug of rigid construction is located axially within tubing in contact with the internal surface of the tubing including the bead. The apparatus includes an eccentrically mounted rotating roller which cooperates with a fixed roller to sequentially apply a compressive force at high frequency and with controlled severity to an external surface of the tubing adjacent the plug. The force moves the plug axially within the pipe a short distance and the plug is then released. The Preusch patent states that the maximum severity of the compressive force or squeezing action must be controlled to prevent the failure of the bearings for the eccentrically mounted roller shaft or the cracking of the product at the weld. It also states that the problem presented due to the variability of the force applied by the squeezing action is complicated by variations in the wall thickness of the tubing being formed, as well as, variations in the height of the weld bead. The internal weld bead in the tubing is removed by axial reciprocation of the plug of the Preusch apparatus.
The present invention relates to a machine in which the weld bead is removed by flattening or blending the bead by hammering it with an external hammer and a mandrel located within the tubing.